System for rate management of aggregate-rate communication services

ABSTRACT

A system for rate management of communication services. The system comprises at least one group of ports sharing a guaranteed-rate; and each of the group of ports determines an allowed-rate using at least one rate management policy.

PRIORITY CLAIM

This application claims the priority of: U.S. Provisional ApplicationNo. 60/758,870, filed on Jan. 13, 2006, “METHOD OF RATE CONTROL FOR ANETHERNET VIRTUAL SHARED MEDIUM” by Robert Sultan; and U.S. ProvisionalApplication No. 60/820,202, filed on Jul. 24, 2006, “SYSTEM AND METHODOF RATE-CONTROL FOR AN ETHERNET VIRTUAL SHARED MEDIUM” by Robert Sultan,Stein Gjessing, Xuan Zhang, Zhushen Deng, Linda Dunbar, Lucy Yong,Jianfei He, and Xixiang Li.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to: U.S. Application No. ______, filedconcurrently with the present application on ______, “SYSTEM FORPROVIDING AGGREGATE-RATE COMMUNICATION SERVICES”, by Robert Sultan, andLinda Dunbar; and U.S. Application No. ______, filed concurrently withthe present application on ______, “SYSTEM FOR RATE-CONTROL OFAGGREGATE-RATE COMMUNICATION SERVICES”, by Robert Sultan, SteinGjessing, Xuan Zhang, Zhusheng Deng, Xixiang Li, and Jianfei He.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to network communications, andmore particularly, to a versatile system for rate management ofaggregate-rate communication services.

BACKGROUND OF THE INVENTION

Ethernet is one of the most widely-installed Local Area Network (LAN)technologies. Users are attracted by a number of advantages of Ethernetservices, including ease of use, cost effectiveness, flexibility, andwide rage of service options, etc. Ethernet services have been extendedto metropolitan areas and beyond.

Ethernet services may vary in many ways. The Metropolitan Ethernet Forum(MEF) defines two types of Ethernet services: E-Line services, which arepoint-to-point services; and E-LAN services, which are multipointservices such that each instance of service shares the use of a commonunderlying physical network. MEF specifies distinct layer-1 and layer-2E-LAN services. A layer-1 E-LAN service is called an Ethernet LAN (ELAN)service, and a layer-2 E-LAN service is called an Ethernet Virtual LAN(EVLAN) service. The EVLAN allows users to exchange frames as ifconnected to a shared medium LAN.

Two methods currently used to specify rate guarantees for EVLAN servicesare port-to-port guarantee and per-port guarantee. Port-to-portguarantee specifies a distinct bandwidth guaranteed for traffic from aspecific port to another specific port. This is a traditional guaranteeprovided in frame relay and private-line services. This method may bemore efficient when port-to-port traffic rate is relatively constant.

Per-port guarantee specifies a distinct bandwidth guarantee for trafficoriginating from each port, without regard to destination ports. Thistype of guarantee is relatively easy to police as only knowledge oflocal port ingress traffic is required.

SUMMARY OF THE INVENTION

The present invention provides a system for rate management ofcommunication services. The system comprises at least oneaggregation-group sharing a guaranteed-rate; and each member port of theaggregation-group determines an allowed-rate using at least one ratemanagement policy.

The present invention also provides methods for distributingcommunication messages among the member ports of the aggregation-group.

The following description and drawings set forth in detail a number ofillustrative embodiments of the invention. These embodiments areindicative of but a few of the various ways in which the presentinvention may be utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an aggregate-rate service model according to thepresent invention; and

FIG. 2 illustrates two rate-control thresholds in the method ofrate-control with premium pricing according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is presented to enable a person skilled in theart to make and use the invention. The general principles describedherein may be applied to embodiments and applications other than thosedetailed below without departing from the spirit and scope of thepresent invention as defined herein. The present invention is notintended to be limited to the embodiments shown, but is to be accordedthe widest scope consistent with the principles and features disclosedherein.

The following terms are used in the description of the present inventionbelow:

Adjustment: A method of allowed-rate assignment used when the sum ofmeasured ingress-rates is sufficiently high that continued ramping ofrates could result in exhaustion of capacity associated with theaggregation-group.

Aggregation-group: The set of ports that share a guaranteed-rate.

Ingress: The direction from a user of a service to a provider of theservice.

Port: The interface by which a user accesses the services of a ServiceProvider Network. Examples are an 802.1ad Provider Edge Bridge (PEB)port or a Metropolitan Ethernet Forum (MEF) User-Network Interface(UNI).

Service Provider Network: A network offering connectivity services tocustomers, for example, an IEEE 802.1ad Provider Bridged Network (PBN)or an MEF Metropolitan Ethernet (MEN).

Ramping: A method of allowed-rate assignment in which the allowed-rateis assigned a value that is larger than the current value of a measuredingress-rate.

Rate-message: A message distributed periodically from a port associatedwith an aggregation-group, to all other ports associated with thataggregation-group, carrying the value of the ingress-rate measured (andpossibly smoothed or filtered) by that port.

Service instance: An instance of the connectivity service offered by aService Provider Network. Connectivity is permitted only between portsassociated with the same service instance. Examples are an IEEE 802.1adService Virtual Local Area Network (SVLAN) or an MEF Ethernet VirtualConnection (EVC).

Notation used in the present invention is described in the following.For notational convenience, the symbol Σ represents

$\sum\limits_{i = 0}^{n}$

unless otherwise specified. I_((i,t)) indicates the value of Iassociated with port i at the end of time interval t.

Other identifiers are as follows:

A_(i) (allowed-rate): The maximum rate at which traffic from a user isadmitted to a service provider network at port i of anaggregation-group. I_(i) always ≦A_(i). O_(i)>A_(i) implies I_(i)=A_(i).

B: The minimum amount by which the value of A_(i) for the next timeinterval should exceed the current value of I_(i) when ramping ofallowed-rates is performed.

C (committed capacity): Capacity committed by a service provider for useby an aggregation-group on a link within a Service Provider Network. Acapacity commitment of C ensures that a specified service guarantee ismet at all times. The service provider may commit less bandwidth than C,and assume a risk that the guarantee will not be met at all times.

d_(ij) (delay): Time period, measured in seconds, beginning when a porti has measured its ingress-rate I_(i), for the most recent timeinterval, and ending when a port j references the corresponding valueR_(i) in computing S.

D (delay): The maximum value of d_(ij) over all port pairs (i, j) in anaggregation-group.

F (sum of offered rates): Sum of the values of offered rate (O_(i)) overall ports i.

G (guaranteed-rate): A provisioned value such that ΣI_(i)≧G wheningress-rates have attained a steady-state.

I_(i) (ingress-rate): Actual (measured) rate of traffic introduced byport i of an aggregation-group. The rate may be low-pass filtered orsmoothed to achieve stability.

O_(i) (offered rate): A traffic rate presented by a user to a serviceprovider at port i of an aggregation-group.

n (number of ports): Number of ports associated with anaggregation-group.

Q: Number of ports in an aggregation-group for which R_(i) exceeds acomputed maximum allowed-rate X.

R_(i): Value of I_(i) most recently received by a local port in arate-message from port i. R_(local) is assigned the current value ofI_(local).

S: Sum of R_(i) over all ports i in an aggregation-group.

S_(max): The maximum value attained by S.

t: A count of the number of elapsed intervals of duration T.

T: A fixed time interval between distribution of a value of I_(i) byport i of an aggregation-group. Re-computation of the allowed-rate isalso performed on this time boundary.

X: The largest value of A_(i) that may be assigned to any port i in anaggregation-group following a rate adjustment.

Referring now to FIG. 1, an embodiment of an aggregate-rate servicemodel (100) is illustrated. A Service Provider Network (110) offersaggregate-rate communication services to a customer (120). Customer(120) is associated with 7 ports, port (131)-(137), to access ServiceProvider Network (110). The 7 ports share one guaranteed-rate G, formingan aggregation-group. Service Provider Network (110) may have anarbitrary topology. Ports in an aggregation-group share capacity of theaggregation-group fairly.

Rate-control algorithms may be used to control ingress-rate of each portwithin the aggregation-group, to ensure aggregate-rate services providedby Service Provider Network (110) comply with a Service Level Agreement(SLA). Each port measures I_(i) during the current time interval t. Atthe completion of the time interval t, a port i, e.g. port (131), maydistribute a rate-message, containing the measured (and possiblysmoothed and/or filtered) ingress-rate value I_(i), together with theidentity of the port i.

Each port within the aggregation-group may receive a rate-messagedistributed by other ports within the aggregation-group. A port, e.g.port (137), receives a rate-message from a sending port following adelay of at most D seconds. The receiving port (137) saves the value ofthe ingress-rate, R_(i), received in a rate-message from a port i.

Thus, each port may obtain ingress-rate information of all other portsin an aggregation-group, and use such ingress-rate information as inputto a rate-control algorithm computing an allowed-rate for the next timeinterval. One embodiment of the rate-control algorithm is to performramping if the sum of rates of all ports in an aggregation-group is lessthan a guaranteed-rate; and perform adjustment if the sum of rates ofall ports in an aggregation-group is greater than or equal to aguaranteed-rate.

Rate management policies may be provided to specify the ways in whichports of an aggregation-group share the capacity of theaggregation-group, and ways to manage capacity requirement of eachindividual port in an aggregation-group. For example, ports associatedwith an aggregation-group may share the capacity of theaggregation-group equally, or proportionally according to a weightingscheme, or the allowed-rate of one port may be set to a predefined valueor restricted to a value that is greater than, or less than, apredefined value. Rate-control algorithms may be used to controlindividual rate and aggregate-rate of an aggregation-group according tothe rate management policy.

Rate-control algorithms may vary according to different rate managementpolicies. One embodiment of rate management policy may be that portmembers of an aggregation-group share a guaranteed-rate fairly, but notequally. This is the case, for example when one port is a high-capacityserver, and other ports are clients. It may be useful to share theguaranteed-rate, but allow the server access to a larger share of theguaranteed-rate.

Using this rate management policy, in one embodiment, each port i may beassigned a weighting factor, W_(i). When an ingress-rate, I_(i), isreported via a rate-message, the reported value is normalized bydividing the reported value by W_(i).

Thus for a local port performing ramping, the term B may be changed toW_(local)B in order to accommodate the weighting factor, and anallowed-rate for the next time interval may be changed to:

A _(local) =I _(local) +W _(local) B.

That is, a port i, sending at rate I_(i) during time interval t, may berestricted by A_(i)=I_(i)+W_(i)B during time interval t+1. In theabsence of delay, this method of ramping would ensure thatΣ_(i)≦G+ΣW_(i)B in time interval t+1, since ΣI_(i)≦G in time interval t,and each port may increase its ingress-rate by no more than W_(i)B.

In the presence of delay D, sufficient additional capacity must exist inorder to account for the delayed arrival of rate-messages. During thetime period D, the ingress-rate of each port, except the local port, mayrise by an additional W_(i)BD/T. Hence, additional capacity ΣW_(i)BD/T(for i≠local) must be committed. Capacity required in the case ofweighted fairness may be expressed as C=G+ΣW_(i)B+ΣW_(i)BD/T (fori≠local in the last item of the expression).

The method of adjustment may also be modified to accommodate theweighting factors. The method of computing the allowed-rate, after thevalue of X has been determined, may be modified as follows:

A _(local)=MIN (I _(local) , W _(local) X)+W _(local) B.

X may be computed iteratively by fractionally increasing, or decreasing,a proposed value of X until the proposed value meets the condition:

G≈ΣR _(i)(for R _(i) /W _(i) <X)+ΣW _(i) X(for R _(i) /W _(i) ≧X).

The capacity requirement may be adjusted as follows to accommodate theweighting factors:

C=G+ΣW _(i) B+ΣW _(i) BD/T(for i≠local in the last item of theexpression).

An alternative rate management policy may be that an access rate of anindividual port may be restricted. For example, the allowed-rate, A_(i),at a port i may be restricted to a value less than G. This is usefulwhen a service provider cannot provide access to a port at the fullguaranteed-rate G, or when a user does not require access at a rategreater than A_(i).

One embodiment for this rate management policy is to apply a restrictrate value P_(local) to a port to be restricted. In this case, the valueof A_(local) for the next time interval in the method of ramping may becomputed as:

A _(local)=MIN (I _(local) +B, P _(local))

for a port whose access is limited to P_(local).

In the case of adjustment, the value of A_(local) for the next timeinterval may be computed as:

A _(local)=MIN (P _(local), MIN (I _(local) , X)+B).

Another alternative rate management policy may be that a user may becharged for aggregate ingress-rate exceeding a threshold. The method ofmonitoring performance of an aggregation-group provides an opportunityto charge a higher rate for services when an aggregate ingress-rateexceeds a pre-determined level, e.g., a threshold. Crossing of thisthreshold may be detected by a performance monitoring application. Thismethod discourages high levels of sustained usage without explicitlypreventing such usage. In one embodiment, a user, when using capacityabove a guaranteed-rate, may indemnify a service provider by paying apremium rate to offset the increased risk associated with exceeding thecapacity committed to the user by the service provider. In this case,the rate-control algorithm is not used to compute the value of policingparameters, but is used to compute when a premium rate is to be charged.

In another alternative rate management policy, the method of premiumpricing for an aggregation-group may be combined with a method ofrate-control by specifying two threshold values. One embodiment is shownin FIG. 2. Under the first threshold—a premium pricing threshold (220),there is no rate control. Area (210) is a base pricing zone. A user paysa first price if the aggregate-rate is within area (210). If a usercrosses premium pricing threshold (220), but is still under the secondthreshold—a rate-control threshold G (240), i.e. within zone (230) inFIG. 2, then the user pays a second price for aggregate ingress-rate inzone (230). Traffic above the second threshold (240), i.e., in zone(250), does not incur additional charges, but is not guaranteed. Trafficin zone (250) may be discarded, or restricted.

The above embodiment not only has the benefit that a user may reducecosts by shaping usage to a level below a premium price threshold, butalso has the flexibility to allow use of bandwidth up to aguaranteed-rate. For a service provider, this embodiment may protectagainst insufficient resource commitment, and allow premium pricing forhigher levels of resource usage.

A rate management policy may provide methods for sharing aguaranteed-rate among ports of an aggregation-group. The method,described in the rate-control algorithms, of apportioning theaggregate-rate among ports is known as a “greedy” method of rateadjustment, as it reduces only the rates of “greedy” (mostrate-consuming) ports, while leaving other ports unaffected. The greedymethod is described by:

G=ΣR _(i)(for R _(i) <X)+ΣX(for R _(i) ≧X).

An alternative policy may be that each port of an aggregation-group isentitled to an equal share or a weighted share of a guaranteed-rate.This may be accomplished by a simple division (or weighted division) ofthe guaranteed-rate among ports as follows:

A_(j)=G/n; or

A _(j)=(W _(j) /ΣW _(j))G.

A second alternative policy may be that ports consuming more capacitymay be assigned a higher allowed-rate when there is contention for aguaranteed-rate among ports. This may be accomplished by arate-proportional division of the guaranteed-rate among ports asfollows:

A_(j)=(R_(j)/ΣR_(i)) G.

A third alternative policy may be that ports whose ingress-rates areless than a mean rate may not adjust their rates. Other ports share theremaining of a guaranteed-rate. This policy may be expressed as follows:

A _(j) =R _(j)(R _(j) ≦G/n); and

A_(j)=(G−sum of R_(i))/Q (R_(i)≦G/n; R_(j)>G/n; where Q is the number ofports whose ingress-rates satisfy R_(j)>G/n.

The method for sharing a guaranteed-rate explicitly includes thealternatives described above, and also methods that are conceptuallysimilar.

The rate management policy and rate-control algorithms requiredistribution of rate-related information associated with each portmember of an aggregation-group. In describing the rate-controlalgorithms and the method of monitoring performance of anaggregation-group, a method is provided for distributing rate-messagesfrom each port to all other ports in the aggregation-group. Arate-message may contain ingress-rate and identity of a distributingport. The distribution may be accomplished by addressing a rate-messageto a Group Media Access Control (MAC) address associated with anaggregation-group. This method is known as a Multicast and is well-knownto practitioners of the art. The Group MAC address associated with theaggregation-group may be provisioned (or configured) at each port.

An alternative embodiment of the method for distributing rate-messagesis to specify an ordering (or sequence) of ports in anaggregation-group. Each port is identified by an Individual MediumAccess Control address established by provisioning (or configuration)Rate-messages may then be sent by a port to the next port in sequence.This method is known as a Unicast and is well-known to practitioners ofthe art. Methods of ordering the ports are well known to practitionersof the art. The ordering may be circular so that the port at the end ofthe sequence sends rate-messages to the port at the beginning of thesequence. The rate-message may be extended to allow the measuredingress-rate of each port in an aggregation-group to be carried,reducing the number of rate-messages that need be circulated, and toallow identification of the aggregation-group. The sequential method maybe used when it is desirable to reduce the number of rate-messagescrossing links in a network, at the expense of some additional delay inthe transfer of rate information.

A second alternative embodiment may allow a port to send rate-messagesin both ascending and descending directions of a sequence. That is,rate-messages are sent in “logically” counter-rotating directions. Thisreduces the delay in receiving rate information, in exchange for acorresponding increase in the total number of transferred rate-messages.In one embodiment, a control-message is sent in each direction of thelogical sequence and carries the rates of approximately half the portsin the aggregation-group.

An additional alternative allows summarization of the rate information.In this case, only a single rate value is sent by a port to itsneighbors in the sequence. This value may be, for example, a weightedaverage of the locally-measured rate and the rate contained in arate-message, as follows:

XmitRateMsg.Rate=(R_(i)+(n−1)*RcvdRateMsg.Rate)/n.

This method is compatible with policies of rate adjustment that do notrequire knowledge of individual measured ingress-rates, as specified, bythe alternative policy for partition of a guaranteed-rate describedabove, in which each port is entitled to an equal share or a weightedshare of the guaranteed-rate.

The methods for distributing rate-messages described in aboveembodiments may also be used distributing other communication messagesamong a group of ports sharing a common rate.

The previous description of the disclosed embodiments is provided toenable those skilled in the art to make or use the present invention.Various modifications to these embodiments will be readily apparent tothose skilled in the art and generic principles defined herein may beapplied to other embodiments without departing from the spirit or scopeof the invention. Thus, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

1. A system for rate management of communication services, comprising:at least one aggregation-group, comprising n ports sharing aguaranteed-rate G; and wherein each port in the aggregation-groupdetermines an allowed-rate using at least one rate management policy. 2.The system of claim 1, wherein the rate management policy comprises:assigning a weighting factor W_(i)(i=1, . . . n), to each port in theaggregation-group; and determining the allowed-rate for each port in theaggregation-group using a rate-control method.
 3. The system of claim 2,wherein the rate-control method comprises, for each local port:computing the allowed-rate as (I_(local)+W_(local)B), wherein B is anamount of rate increase, I_(local) is an ingress-rate of the local port,and W_(local) is the weighting factor of the local port, if sum ofingress-rates of the aggregation-group is less than the guaranteed-rate.4. The system of claim 2, wherein the rate-control method comprises, foreach local port: computing the allowed-rate as MIN(I_(local),W_(local)X)+W_(local)B, if sum of the ingress-rates of theaggregation-group is greater than or equal to the guaranteed-rate,wherein X satisfies G≈ΣR_(i)(for R_(i)/W_(i)<X)+ΣW_(i)X (forR_(i)/W_(i)≧X), B is an amount of rate increase, R_(i) is aningress-rate of port i received in a rate-message from port i, I_(local)is an ingress-rate of the local port, and W_(local) is the weightingfactor of the local port.
 5. The system of claim 2, wherein theworst-case capacity required to support communications among ports ofthe aggregation-group is (G+ΣW_(i)B), in the absence of delay, and B isan amount of rate increase.
 6. The system of claim 2, wherein theworst-case capacity required to support communications among ports ofthe aggregation-group is (G+ΣW_(i)B+ΣW_(i)BD/T) (for i≠local in thethird part of the expression), in the presence of delay D, wherein T isa time period between successive computations of the allowed-rate, and Bis an amount of rate increase.
 7. The system of claim 1, wherein therate management policy comprises: determining the allowed-rate using arate-control method; and restricting the allowed-rate not to exceed apredefined value.
 8. The system of claim 7, wherein the rate-controlmethod comprises, for each local port: computing the allowed-rate asMIN(I_(local)+B, P_(local)), if the sum of ingress-rates of ports withinthe aggregation-group is less than the guaranteed-rate, wherein B is anamount of rate increase, P_(local) is a predefined maximum allowed-ratevalue for the local port, and I_(local) is an ingress-rate of the localport.
 9. The system of claim 7, wherein the rate-control methodcomprises, for each local port: computing the allowed-rate asMIN(P_(local), MIN(I_(local), X)+B), if sum of the ingress-rates of allports is greater than or equal to the guaranteed-rate, wherein Xsatisfies G=ΣR_(i) (for R_(i)<X)+ΣX (for R_(i)≧X), B is an amount ofrate increase, R_(i) is an ingress-rate of port i received in arate-message from port i, P_(local) is a predefined value for the localport, and I_(local) is an ingress-rate of the local port.
 10. The systemof claim 1, wherein a the rate management policy comprises: setting athreshold for the aggregation-group; and charging the customerassociated with the aggregation-group a different rate if theaggregate-rate of the aggregation-group exceeds the threshold.
 11. Thesystem of claim 10, wherein aggregate-rate of the aggregation-group ismonitored by a performance monitoring application.
 12. The system ofclaim 1, wherein the rate management policy comprises: setting a firstthreshold and a second threshold for the aggregation-group; charging afirst price to the customer associated with the aggregation-group, ifthe aggregate-rate of the aggregation-group is under the firstthreshold; and charging a second price to the customer associated withthe aggregation-group, if the aggregate-rate of the aggregation-groupexceeds the first threshold and is less than the second threshold. 13.The system of claim 12, further comprising discarding traffic associatedwith the aggregation-group if the aggregate-rate of theaggregation-group exceeds the second threshold.
 14. The system of claim12, further comprising restricting traffic associated with theaggregation-group if the aggregate-rate of the aggregation-group exceedsthe second threshold.
 15. The system of claim 1, wherein the ratemanagement policy comprises each port of the aggregation-group sharingthe guaranteed-rate G equally: A_(j)=G/n, (j=1, . . . n), wherein A_(j)is the allowed-rate of port j.
 16. The system of claim 1, wherein therate management policy comprises each port of the aggregation-groupsharing the guaranteed-rate G based on a weighting factor:A_(j)=(W_(j)/ΣW_(j))G, (j=1, . . . n), wherein W_(j) is the weightingfactor of port j, and A_(j) is the allowed-rate of port j.
 17. Thesystem of claim 1, wherein the rate management policy comprises eachport of the aggregation-group sharing the guaranteed-rate Gproportionally to capacity consumed by each port:A _(j)=(R _(j) /ΣR _(j))G, (j=1, . . . n) wherein R_(j) is aningress-rate of port j received in a rate-message from port j, and A_(j)is the allowed-rate of port j.
 18. The system of claim 1, wherein therate management policy comprises ports, whose ingress-rate is greaterthan a mean rate, sharing the remaining of the guaranteed-rate G,subtracted by the sum of ingress-rates of ports, whose ingress-rate isless than or equal to the mean rate:A _(j) =R _(j)(R _(j) ≦G/n); andA _(j)=(G−sum of R _(i))/Q (R _(i) ≦G/n; R _(j) >G/n) (j=1, . . . n),wherein Q is the number of ports whose ingress-rates satisfy thatR_(j)>G/n, R_(j) is an ingress-rate of port j received in a rate-messagefrom port j, and A_(j) is the allowed-rate of port j.
 19. The system ofclaim 1, wherein the ports of the aggregation-group share theguaranteed-rate fairly.
 20. The system of claim 1, further comprising anetwork providing the communication services, the network having anarbitrary topology.
 21. A method of distributing communication messagesamong a group of ports sharing a guaranteed-rate fairly, in acommunication network with an arbitrary topology, comprising the stepsof: forming a sequence using the group of ports with a specified order;and each of the group of ports sending communication messages accordingto the order.
 22. The method of claim 21, wherein the communicationmessages comprise a rate-message.
 23. The method claim 22, wherein therate-message contains ingress-rate information and identity of thesending port.
 24. The method of claim 22, wherein the rate-messagecontains ingress-rate information of each of the group of ports.
 25. Themethod of claim 22, wherein the order is specified such that each of thegroup of ports sends rate-messages to next port in the sequence.
 26. Themethod of claim 25, wherein a rate-message is addressed to an individualMedia Access Control address.
 27. The method of claim 25, wherein theorder of the group of ports is circular such that the port at the end ofthe sequence sends rate-messages to the port at the beginning of thesequence.
 28. The method of claim 22, wherein the order is specifiedsuch that each of the group of ports sends rate-messages to a next portin both ascending and descending directions of the sequence.
 29. Themethod of claim 22, wherein the order is specified such that each of thegroup of ports sends rate-messages to adjacent ports in the sequence,and each rate-message comprises one rate value.
 30. The method of claim29, wherein the rate value is a weighted average of a locally-measuredrate and rates contained in a rate-message.
 31. A system for ratemanagement of aggregate-rate services, comprising: at least oneaggregation-group comprising n ports sharing a guaranteed-rate G fairly;wherein each of the group of n ports is assigned a weighting factorW_(i)(i=1, . . . n); and wherein each port of the aggregation-groupdetermines an allowed-rate using a rate-control method.
 32. The systemof claim 32, wherein the rate-control method comprises, for each localport: computing the allowed-rate as (I_(local)+W_(local)B), if sum ofingress-rates of the aggregation-group is less than the guaranteed-rate;computing the allowed-rate as (MIN(I_(local), W_(local)X)+W_(local)B),if sum of the ingress-rates of the aggregation-group is greater than orequal to the guaranteed-rate; and wherein B is an amount of rateincrease, I_(local) is an ingress-rate of the local port, W_(local) isthe weighting factor of the local port, X satisfies G≈ΣR_(i) (forR_(i)/W_(i)<X)+ΣW_(i)X (for R_(i)/W_(i)≧X), R_(i) is the ingress-rate ofport i received in a rate-message from port i, and W_(i) is theweighting factor of port i.